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[BIP-119] Use mediawiki syntax highlighting, add comment to spec
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Jeremy Rubin
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b1791c24aa
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@ -167,31 +167,40 @@ OP_CHECKTEMPLATEVERIFY as implemented in C++ in the context of Bitcoin Core can
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be seen in the reference implementation.
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The execution of the opcode is as follows:
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def execute_bip_119(self):
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# Before soft-fork activation / failed activation
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if not self.flags.script_verify_default_check_template_verify_hash:
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# Potentially set for node-local policy to discourage premature use
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if self.flags.script_verify_discourage_upgradable_nops:
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return self.errors_with(errors.script_err_discourage_upgradable_nops)
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return self.return_as_nop()
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# CTV always requires at least one stack argument
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if len(self.stack) < 1:
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return self.errors_with(errors.script_err_invalid_stack_operation)
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# CTV only verifies the hash against a 32 byte argument
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if len(self.stack[-1]) == 32:
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# Ensure the precomputed data required for anti-DoS is available,
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# or cache it on first use
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if self.context.precomputed_ctv_data == None:
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self.context.precomputed_ctv_data = self.context.tx.get_default_check_template_precomputed_data()
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if stack[-1] != self.context.tx.get_default_check_template_hash(self.context.nIn, self.context.precomputed_ctv_data)
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return self.errors_with(errors.script_err_template_mismatch)
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return self.return_as_nop()
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# future upgrade can add semantics for this opcode with different length args
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# so discourage use when applicable
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<source lang="python">
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def execute_bip_119(self):
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# Before soft-fork activation / failed activation
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# continue to treat as NOP4
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if not self.flags.script_verify_default_check_template_verify_hash:
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# Potentially set for node-local policy to discourage premature use
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if self.flags.script_verify_discourage_upgradable_nops:
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return self.errors_with(errors.script_err_discourage_upgradable_nops)
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else:
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return self.return_as_nop()
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return self.return_as_nop()
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# CTV always requires at least one stack argument
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if len(self.stack) < 1:
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return self.errors_with(errors.script_err_invalid_stack_operation)
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# CTV only verifies the hash against a 32 byte argument
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if len(self.stack[-1]) == 32:
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# Ensure the precomputed data required for anti-DoS is available,
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# or cache it on first use
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if self.context.precomputed_ctv_data == None:
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self.context.precomputed_ctv_data = self.context.tx.get_default_check_template_precomputed_data()
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# If the hashes do not match, return error
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if stack[-1] != self.context.tx.get_default_check_template_hash(self.context.nIn, self.context.precomputed_ctv_data)
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return self.errors_with(errors.script_err_template_mismatch)
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return self.return_as_nop()
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# future upgrade can add semantics for this opcode with different length args
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# so discourage use when applicable
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if self.flags.script_verify_discourage_upgradable_nops:
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return self.errors_with(errors.script_err_discourage_upgradable_nops)
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else:
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return self.return_as_nop()
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</source>
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The computation of this hash can be implemented as specified below (where self
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is the transaction type). Care must be taken that in any validation context,
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@ -202,46 +211,50 @@ including hashes of the scriptsigs, sequences, and outputs. See the section
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"Denial of Service and Validation Costs" below. This is not a performance
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optimization.
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def get_default_check_template_precomputed_data(self):
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result = {}
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# If there are no scriptSigs we do not need to precompute a hash
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if any(inp.scriptSig for inp in self.vin):
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result["scriptSigs"] = sha256(b"".join(ser_string(inp.scriptSig) for inp in self.vin))
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# The same value is also pre-computed for and defined in BIP-341 and can be shared
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result["sequences"] = sha256(b"".join(struct.pack("<I", inp.nSequence) for inp in self.vin))
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# The same value is also pre-computed for and defined in BIP-341 and can be shared
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result["outputs"] = sha256(b"".join(out.serialize() for out in self.vout))
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return result
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<source lang="python">
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def get_default_check_template_precomputed_data(self):
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result = {}
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# If there are no scriptSigs we do not need to precompute a hash
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if any(inp.scriptSig for inp in self.vin):
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result["scriptSigs"] = sha256(b"".join(ser_string(inp.scriptSig) for inp in self.vin))
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# The same value is also pre-computed for and defined in BIP-341 and can be shared
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result["sequences"] = sha256(b"".join(struct.pack("<I", inp.nSequence) for inp in self.vin))
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# The same value is also pre-computed for and defined in BIP-341 and can be shared
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result["outputs"] = sha256(b"".join(out.serialize() for out in self.vout))
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return result
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# parameter precomputed must be passed in for DoS resistance
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def get_default_check_template_hash(self, nIn, precomputed = None):
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if precomputed == None:
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precomputed = self.get_default_check_template_precomputed_data()
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r = b""
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# pack as 4 byte signed integer
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r += struct.pack("<i", self.nVersion)
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# pack as 4 byte unsigned integer
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r += struct.pack("<I", self.nLockTime)
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# we do not include the hash in the case where there is no
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# scriptSigs
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if "scriptSigs" in precomputed:
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r += precomputed["scriptSigs"]
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# pack as 4 byte unsigned integer
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r += struct.pack("<I", len(self.vin))
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r += precomputed["sequences"]
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# pack as 4 byte unsigned integer
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r += struct.pack("<I", len(self.vout))
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r += precomputed["outputs"]
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# pack as 4 byte unsigned integer
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r += struct.pack("<I", nIn)
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return sha256(r)
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# parameter precomputed must be passed in for DoS resistance
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def get_default_check_template_hash(self, nIn, precomputed = None):
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if precomputed == None:
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precomputed = self.get_default_check_template_precomputed_data()
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r = b""
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# pack as 4 byte signed integer
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r += struct.pack("<i", self.nVersion)
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# pack as 4 byte unsigned integer
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r += struct.pack("<I", self.nLockTime)
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# we do not include the hash in the case where there is no
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# scriptSigs
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if "scriptSigs" in precomputed:
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r += precomputed["scriptSigs"]
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# pack as 4 byte unsigned integer
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r += struct.pack("<I", len(self.vin))
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r += precomputed["sequences"]
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# pack as 4 byte unsigned integer
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r += struct.pack("<I", len(self.vout))
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r += precomputed["outputs"]
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# pack as 4 byte unsigned integer
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r += struct.pack("<I", nIn)
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return sha256(r)
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</source>
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A PayToBareDefaultCheckTemplateVerifyHash output matches the following template:
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# Extra-fast test for pay-to-basic-standard-template CScripts:
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def is_pay_to_bare_default_check_template_verify_hash(self):
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return len(self) == 34 and self[0] == 0x20 and self[-1] == OP_CHECKTEMPLATEVERIFY
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<source lang="python">
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# Extra-fast test for pay-to-basic-standard-template CScripts:
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def is_pay_to_bare_default_check_template_verify_hash(self):
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return len(self) == 34 and self[0] == 0x20 and self[-1] == OP_CHECKTEMPLATEVERIFY
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</source>
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==Deployment==
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